Telephone-exchange system.



A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. I7. 1915.

Patented Jan. 8,1918.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. l7. l9l5.

Patented Jan. 8,1918.

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TELEPHONE EXCHANGE SYSTE M.

APPLICATION EILEI) DEC. IT. I915 Patented Jan. 8,1918.

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A. E. LUNDELL.

TELEPHONE EXCH/WGE SYSTEM. AFPUCAT'ION mm Maul. 1915. r 1,252,461 Patented. Jan. 8,1918"),

A.,E. LUNDELL. TELEPHONE EXCHANGE SYSTEM 4 APPLICATION FILED DEC-I'L19l5- 1,252,461. Patented Jan.48,1918.

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AIBEN IE. LUNDELL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

' INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed December 17, 1915.

semi-automatic telephone systems in which connections may be established through a, plurality of manual and automatic ofiices between two subscribers stations.

It is the object of this invention to provide an arrangement whereby a line extended through a connecting circuit is rendered idle if a certain connection is desired thereto.

According to the main feature of this invention, means are provided for automatically rendering idle a calling line, if an operator engaged in extending this calling line to a called line desires to again seize the former, whereby this engaged line will test idle.

The drawings represent a semi-automatic telephone exchange system. Figures 1, 2, 3 and 4 should be placed side by side in the named order, and Fig. 5 below Fig. 1.

In general terms, the operation of the system is as follows: Upon the removal of the receiver at a substation 100, a connecting operator, located at an office in which this lirie terminates, inserts her plug 103 into jack 101. A characteristic potential is thus placed on the calling line for rendering it inaccessible to incoming calls, and said line is extended to a connecting circuit. The connecting operator after having learned from the calling subscriber the number of his line and the number of the line wanted if the desi-od line has to be reached through a toll line, instructs the subscriber to hang up his receiver, and proceeds to extend the connecting circuit by means of selectors 111 and 200 to a trunk leading to another olhce and there terminating in a jack 205. However, if the operator thinks that the desired connection may be established within a short time, she will leave the subscriberon the line.

A toll operator located at the other oilice has a cord circuit 239 by means of which she extends the connecting circuit through a jack 208 to an incoming operators position, located at the first mentioned office. this jack being preferably assigned for use by the in- Specification of Letters Patent.

Patented Jan. ,8, 1918.

Serial No. 67,411.

coming operator through an order wire (not shown). The incomingoperator established then, under the control of her impulse sender shown in the lower right-hand corner of Fig. 3, a connection through selector switches 327 and 400 to the calling substation 100, relay 105 being provided to remove the busy test condition from the sleeve wire of this line. After this line has been seized, the toll operator removes her plug 201 from jack 205 and inserts it in the multiple jack connected to the called subscribers line (not shown), causing thereby in any well-known manner the release of selector switches 200 and 111. The connecting operator then removes plug 103 from jack 101, and the calling subscriber may converse with the called subscriber through connector 400, selector 327 and the toll operators cord circuit 209.

A clearer understanding of this invention may be had from the following detailed description and appended claims.

The subscriber at substation 100, desiring to obtain a connection, removes his receiver from the switchhook, causing thereby the energization of the line relay 101, which in turn causes the lighting of a calling lamp 102. The connecting operator noticing the signal inserts her plug 103 into an answering terminal of the calling line, such as jack 101. As well known, a plurality of such answering terminals are provided to which the calling line is connected in multiple. A test circuit is closed thereupon from ground through'the armature and back contact of relay 105, the winding of a relay 106, the sleeve contacts of plug 103 and jack 101, and the winding of a cut-off relay 107 to ground ed battery. The cut-off relay 107 by' attracting its armatures opens the circuit of 'line 101, whereupon the lamp 102 is extinguished. The operator may converse now with the calling subscriber in the wellknown manner. Having learned the number of his line and that of the desired station, she instructs him to restore his receiver and adjusts her sender. shown in Fig. 5. The sender is of the revertive impulse type in which a stepping magnet 508, controlled by impulses sent back from selector switches 111 and 200, causes the release of the sender to normal position, the impulse receiving circuit being open at contact 510 after the sending out of each set of impulses. A complete description of the operation of such senders may be had from my Patent No. 1,168,319,

issued January 18, 1916. It will be obvious, however; to those skilled in the art that instead of senders disclosed in the patent referred to, sending devices of widely varying character may be em loyed without departing from the spirit of the present invention. Obviously, other types of switches than the one disclosed must be used with certain senders.

The connecting operator has a plurality of keys by means of which the sender maybe adjusted. Only one of such keys, 500, is shown in Fig. 5.

Upon the depression of key 500, a circuit is closed from the plus pole of battery through key contact 501, conductor 115, contact 116, and the power magnet of a sequence switch 117, to the minus pole of batte'ry. Under the control ofa normal spring 118, the sequence switch is caused to move jou t, of position 1 into position 13. It will ,be noted at this point that in order to con- 'trol the establishment of other than toll,

calls, key 500 would not be depressed. An assignment key is used in this case for moving sequence switch 117 through a plurality of operating positions into position 13,-

In positions 1'12 of the sequence switch, .the selective operation of selectors 111 and 200 is controlled. .Due to the closure of keycontact 502, a circuit is closed through con- I tact 503;,and the power magnet of a sender sequence switch 504, and under the control 'offa normal spring 520 this switch is moved out ofposit1on1 into 2. An impulse controlling circuit. is. closed now through contacts 120 and 121 (in position 11) of sequence switch 117,-conductors 505 and 506, the winding of stepping magnet 508, se-

quence switch contact 509 and contact 510 sequence switch spring 512, a closed keycontact 513 andthewinding of a counting relay 514 to grounded-battery. Relay 514 hccomcs energized and closes through its contact and sequence switch contact 515:).

circuit for relay 511. Upon the denergiza tion of magnet 508, a shunt placed on the winding of relay 511 through the contact of magnet 508 is removed. This relay becomes energized and opens at contact 510 the confi 'qlling-circuit, and closes a circuit from ground through its right-hand amature and meth ne-a 516 magnet of sequence switch 504 to grounded battery. This sequence switch is moved out of position 2 into position 4, relays 514 and desired set of terminals, a circuit is closed from ground through the test brush of this selector, the armature and back contact of a relay 201 and the winding of relay 202, to grounded battery, and this relay causes the lighting of a lamp 203 at the toll oflice. A toll operator, by inserting her plug 204 into the jack 205 in which the trunk seized by the selector 200 terminates, causes the energization of cut-ofi? relay 201, which in turn opens the circuit of relay 202, extinguishing thereby lamp 203. The toll operator c0n nects her telephone set 206 to cord circuit 209 by depressing listening key 207, and inquires the number of the desired subscriber from the connecting operator.

Upon the depression of listening key 207, a circuit is closed from grounded batteryv through the secondary winding of a repeating coil 130, the winding of a supervisory relay 131, sequence switchcontact 132, selectors 111 and 200, the ring contacts of jack 205 and plug 204, a retardation coil 210, the left-hand back contact and armatureof relay 211 and key contact 212 to ground. Relay 131 becomes energized and closes a circuit from the plus pole of battery through its front contact and armature, contact 133 and the power magnet of sequence switch 117 to the minus pole of battery. Due to the closure of this circuit, the sequence switch is moved out of position 13 into position 14.

In this position ofthe sequence switch a eircuit is closed from the plus pole of battery through key contact 521, conductor 522, the winding of relay 105 sequence switch contacts 135 and 136, resistances 137 and 139 and contact 134 to ground. Relay 105, however, does not become energized, plus battery being connected to its winding through the armature and front contact of relay 131 and s'equence switch contact 135. r A lamp 138 is prevented from lighting due to the closure of a shunt from the plus pole of battery through this lamp, resistance 137, contact 136 and the armature and front contact of relay 131 to the plus pole of batter-v. I

Having learned the number of the subscribcr Wanted, the toll operator confers, by means of an order wire (not shown), with an incoming operator located at the office in which, the calling line terminates, who assigns for uses trunk, such as trunk 305, 306, terminating in a jack 208 at the toll operators position. The toll operator then inserts plug 207 into this jack, es

tablishing a circuit from the plus pole of battery through the sleeve contacts of jackwinding of a relay 214, ring contacts of plug- 207 and jack 208. conductor 306. contact 308 of relay 302, and the lower winding of relay 300 to ground.

Relay 300, which has been energized sin'iultaneously with relays 214 and 213, closes a circuit, on one hand, from ground through its armature and the winding of relay-309, to grounded battery, for energizing this relay, and on the other hand, through sequence switch contact 319 and the winding of relay 302, to grounded battery. Relay 302 upon energization, opens at its contacts 301 and 308 the circuit of relays 214 and 300; relay 214 becomes det nergized; relay 300, however, stays energized by a circuit extending from grounded battery, through its upper armature, resistance 363, the lower armature and front contact of relay 302, and the lower winding of relay 300, to ground. Helay 213 being slower to attract its armature than relay 214, no circuit-will be established for relay 211, and relay 131 remains energized.

The incoming'operator proceeds now to extend the connecting circuit back to the calling subscribers line. First, she depresses her assignment key 310, closing a circuit from ground through this key, contact 311, and the power magnet of a sequence switch 312 to grounded battery. Sequence switch 312 leaves itsfirst position and moves, under the control of a normal spring 313, into position 13. In position 2 of sequence switch 312, a circuit is closed from ground through sequence switch contact 314, contact 315 of sequence switch 316, and the winding of a relay 317 to grounded battery. Relay 317 upon energization closes a circuit through its armature and front contact, and contact 313 and power magnet of sequence switch 316 to grounded battery. This sequence switch is under the control of its normal spring 320, moved into position 13. After sequcncc switch 316 leaves its first position, relay 317 is maintained energized by a circuit closed through contacts 321 and of sequence switches 316 and 312 respectively. .Whilc sequence switch 316 is moving from iosilion 1 to 13. circuits are established for .causing a cord finder to hunt with its wiping line, and causes, in the well-known manner, selector switch 327 to engage with its wipers 328, 329 and 330, the contacts in which terminates trunk 401, 402 and 403 leading to a filial selector or connector 400. The setting of the selector switch 327 is accomplished before sequence switch 312 reaches position 13. The operation of the sender shown in the lower right-hand corner of Fig. 3. is like the one disclosed in the mentioned Patent No. 1,168,319. The sequence switch 316 is shown as accomplishing the functions of sequence switches 400 and 300 of the mentioned patent. Relay 338 is the upper zcro counting relay and corresponds to relay 403 (Fig. 3) of Patent No. 1,168,319.

In position 12 of sequence switch 312 and position 13 of sequence switch 316, a circuit is closed from grounded battery through the coil of a relay 331, sequence switch contacts 332 and 333, conductor 326, cord finder brush 324, sequence switch contacts 334 and 335, resistance 336, windings of a stepping magnet 337, and backcontact and armature of relay 338 to ground. Relay-331 by attracting its right-hand armature prepares a locking circuit. for itself, and when sequcnce switch 312 reaches its 13th position, this locking circuit is completed through sequence switch contact 340.

lVlien the wipers of selector switch 327 are set, a circuit is closed from ground, through the left-hand armature and front contact of relay 331-, sequence switch contact 341, wiper 328, conductor 401, sequence switch contacts 404 and 405, conductor 406, and the winding of relay 407 to grounded battery. Relay 407 becomes energized and closes a circuit from ground through its left-hand arn'lature and front contact, contacts 408 and 400 of sequence switch 410, and the winding of relay 411 to grounded battery. Relay 411 upon energization causes sequence switch 410 to move from position 1 into 6, by closing a circuit from ground through its leftshand arimiture and front contact,contact 412, and the power magnet of sequence switch 410 togrounded battery. llclay 411 does not become deiinergized when the sequence switch leaves its first position, as this relay established a locking circuit for itself from grounded battery through its winding, front contact and right-hand armatur a resistance 413, test conductor 403, wiper 330, a resistance 342 and sequence switch contact 343 to ground. Due to the closure of this circuit, the potential on the terminal of conductor 403 is reduced to guard the trunks selected by switch 327 against seizure by other selector switches. Relay 407 remains also energized when sequence switch 410 leaves its first position, a circuit being closed from grounded battery through the winding of this relay, conductor 406, sequence switch contact 414, front contact and right-hand armature of relay 407, sequence switch contacts 415 and404, conduotor 401, wiper 328, contact 341 of sequeries switch 312, and the front contact and left armature of relay 331 to ground.

In positionfi of mquence switch 410, a circuit is closed for elmIating-magnet 41 6 of connector 400 from grounded battery through the winding of this magnet, conductor 417, sequence switch contact 418, front contact and right armature of relay 407, sequence .switch contacts 415 and 404, conductor 401, wiper 328, sequence switch contact 341, and the front contact and left armature of relay 331 to ground. The elevating magnet 416 attracts its armature 419 and presses brush rod 420 against a roller 421 which is constantly rotating in the direction indicated by an arrow. Line wipers 422 and 423, the test wiper 424, and brushes 425, 426 and 427 carried by rod 420 are, un-

der the control of roller 421, caused to move in an upward direction. The wipers are adapted to engage calling terminals of sub-- scribers lines provided in a terminal bank 428, and the brushes are adapted to engage segments of a commutator plate-429. The calling line terminals through which subscribers lines may be seized, are multipled to similar terminals provided in the banks of other connector switches.

lVhen brush 425 engages a conducting segment in response to each step taken by the brush, magnet 337 is short circuited and causes upon its de'e'nergization the step-bye step release of the impulse sending arrangement set by the incoming operator. This short circuit may be traced from ground through the armature and back contact of relay 338, .windings of magnet 337, resistance 336, sequence switch contacts 335 and 334, cord finder brush 324, conductor 326,

sequence switch contacts 333 and 345, wiper 329, trunk conductor 402, sequence switch contacts 430 and 431, conductor 432, conducting segment 433, brushes 425 and 427, conducting segment 434, conductor 435, sequence switch contact 436, conductor 437, and the front contact and left armature of relay 407 to ground.

After the impulse sending mechanism has returned to normal and thus the wipers of connector 400 have been moved a number of steps as determined by the set position of' the impulse sending mechanism, a circuit (not shown) is closed for relay 338. Relay 338 attracts its armature and causes sequence switch 316 to move out of position 13 into position 16. A circuit is now closed from ground through sequenceswitch contact 346, cord finder brush 323,"conduetor 325, con tact 347 and the power; magnet of sequence switch 312 to grounded battery, and this sequence switch is Inoae'dinto its fourteenth position.

manner gization reestablishes the circuit including relays 300 and'214, The contact of relay 213 being .closed at this time, relay 211 becomes energized, opens at its left-hand contact the circuit of, relay 131 and closes at its right-hand-contact a circuit for a slow-to-pull-up relay'215. Relay 131 is deenergized during the period of time elapsing between the attraction of the armatures of uick relay 211 and slow relay 215. As the s nut is removed now from relay 105 and lamp 138,both become actuated. Relay 105 opens the circuit of relays 106 and 107. These relays become de'nergized and the electrical condition of the calling line is thus reduced to normal, rendering it accessible to incoming calls. Upon the denergization of relay 107, if the calling subscriber did not hang up his receiver, relay 101 becomes energized and lights the lamp 102, and the operator willknow that a call has been extended back to the calling substation. Lamp 138 will be extinguished upon the energization o1 relay 131, and lamp 102 upon the energization of relay 107 after the line has been seized by connector 400, Lamp 102 will be lighted for a very shortperiod, the seizure of the line by the connector immediately following the energization of re- 1ay'105 is will readily appear.

the calling line number given by the subscriber is not correct, another subscribers line will be seized by connector 400, and therefore lamp 102 will be lighted until relay 107 again becomes energized due to the denergization of relay 105. The connecting operator noticing that lamp 102 is lighted for the same period of time as lamp 138, will know that another line than the desired calling line has been seized, and will cause the severing of this connection and the building up of another connection.

Sequence switch 312 is driven out of posi tion 14 into position 16 by a circuit closed from ground through sequence switch contact 348, conductor 349, the armature and front contact of relay 309, contact 350and the power magnet of sequence switch 312 to grounded battery. The locking circuit of relay 331 is opened upon the restoration of the sender, and relay- 331 in turn opens the energizing circuit of the elevating magnet of connector 400,-the circuit of the latter being open also at sequence switch contact 341. The circuit of relay 317 is opened at contact 322. This relay becomes denergized and drives sequence switch 316 into its normal position, the circuit being closed from ground through the armature and back contact of relay 317, contact 351, and the power magnet of sequence switch 316 to grounded battery. When sequence switch oosition rela 407 is a ain ener ized b a 9 y a c:

circuit closed from the minus pole of battery through the winding of this relay, conductor 406, sequence switch contacts 405 and 404, conductor 401, wiper 328, sequence switch contact 352, the upper back contact of relay 353 and winding 354 of repeating coil 304 to the plus pole of battery and ground. The energization of relay 407 causes sequence switch 410 to move into position 8, the circuit being closed through the left-hand armature and front contact of relay 407 and sequence switch contacts 408 and 441.

Due to thedeenergization of magnet 416,

., the wipers of connector 400 are arrested on the contacts in which the calling subscribers line terminates. The brush rod 420, with the wipers, is maintained in, its advanced position by a spring-pressed pawl 442 adapted to engage openings in rod 420.

If full battery potential exists on multiple test terminal 443, 2'. e. if the above traced test circuit is open, test relay 444 becomes energized, a circuit being established from grounded battery through the winding 0 cut-off relay 107, test conductor 140, terminal 443, wiper 424, sequence switch contact 445, low resistance winding of the marginal test relay 444, sequence switch contacts 446 and the high resistance winding of relay 444 to ground. Relay 44-1 closes a locking circuit for itself from ground through its upper armature, front contact and low resistance winding, sequence switch contact 445 and then through relay 107 to grounded battery; the high resistance Winding of this relay being short-circuited upon the closure of thisshort circuit. The closure of this locking circuit reduces the potential on the multiples of test terminal 443 so as to prevent another test relay 444 from becoming energized, when the connector, with which it is associated, engages the calling terminals of the calling line, and thereby causing this line to test busy at its multiple answering and calling terminals. Relay 107 upon energization causes the extinguishing of lamp 102.

Relay 444 closed from being energized, a circuit is ground through the lower armature and front contact of this relay,

conductor 447, contact 448 and the power magnet of sequence switch 410 to grounded battery. Sequence switch 410 moves out of position 8 into position 16.

When sequence switch 312 came into posltion 16, a circuit was closed from grounded battery, through sequence sw itch contact 339, the winding of relays 355 and 353. sequence switch contact 356 and front contact and armature of relay 300 to ground. Relay becomes energized. Relay 355, however, remains denergized, its winding being shunted through its armature and back contact, and the armature and back contact of a ringing relay' 357. \Vhen sequence switch 410 comes into position 16, ringing current is applied to the calling line from ground through the upper armature and front contact of relay 353, sequence switch contact 352, the talking conductors (indicated in heavy lines), thebell at the subscribers station 100, sequence switch contacts 470, 430 and 35S, bottom armature and front contact of relay 353, sequence's'witch contact 359, winding of ringing relay 357 and ringing current generator 360 to ground. Relay 357 does not become energized until the subscriber at substation 100 removes his receiver from the switchhook. Upon the energization of relay 357, the shunt is removed from relay 355, and this relay becomes energized and closes a 'shunt around relay 353.

The armature of relay 215 is attracted after the cal-ling station 100 has been seized by connector 400, and this relay becomes energized and closes the circuit of relay 131, which in turn places a shunt around relay 105 and lamp 138. The calling line is thus again rendered busy.

Upon the restoration of the armatures of relay 353, the talking conductors are closed at the back contacts of this relay and the circuit of relay 357 is opened. Relay 355 is maintained energized by a circuit from grounded battery through sequence switch contact 339, the winding, armature and front contact of relay sequence switch contact 356, conductor 361, and the armature and front contact of relay 300 to ground. Supervisory relay 362 also became energized upon the closure of the talking circuit at the called station, after relay 353 released its armatures. A circuit is now closed from ground through the armature and front contact of relay 300, front contact and armature of relay 362, and the winding of relay 302 to grounded battery. Upon the energization of relay 302, the circuit of relays 214 and 300 is opened, but relay 300 is maintained energized in the above described manner. Due to the decnergization of relay 214, relays 211 and 215 become de'energized; relay 131, however, remains energized. Relay 214 may now actuate a well known supervisory signal (not shown), indicating to the toll operator that the calling line is ready 'for extension to the desired distant station. She will pull plug 204 out of jack 205, causing thereby, in a -wellknown manner, the release of selectors 200 and 111, and will establish the connection by inserting plug 204 into a jack (not shown) in which the called line terminates. In the wellknown manner a signal will be conveyed to the connecting operator, whereupon she will pull a plug 103 out of jack 104.

After the conversation is finished and the calling subscriber hangs up his receiver, relay 362 becomes denergized and deenergizes in turn relay 302. Upon the release of the armature of relay 302, the winding of relay 300 is again included in its original energizing circuit, and relay 2114 thereby causes again the actuation of the above mentioned supervisory signal. The operator controlling the cord circuit 209 pulls plug 207 out 0 jack 208, causing thereby relays 213, 214 and 300 to release. Relay 300 upon deenergization, opens the circuit of relay 309, which, by retracting its armature closes a circuit from ground through sequence switch contact 348, conductor'349, armature and back contact of relay 309 and the winding of relay 370,,which is slow to energize, to grounded battery. Relay 370 closes then a circuit from ground through contacts 371, 372 and the power magnet of sequence switch 312 to grounded battery, and this sequence switch is moved over its 18th into its first position. In positions 17 and 18 of the sequence switch, selector 327 is restored to normal in the well-known manner.

When the brush 330 of selector 327 disengages the terminal of conductor 403, relay 411 becomes denergized and closes a circuit from ground over its armature and back contact, contact 450 and the power magnetof sequence switch 410 to grounded battery, andthis sequence switch is moved into its 18th position. When sequence switch 410 leaves position 16, the circuit of test relay 444 is opened at 445, and this relay becomes deenergized. Further, a circuit is closed from p grounded battery, through the winding of a release magnet 451, conductor 452 and sequence switch contacts 453, 454 to ground. Magnet 451 attracts its armature 455. causing thereby pawl 442 to disengage brush rod and presses the brush rod against re r 456 constantly rotating in a counterclockwise dircction. The roller 456 moves the brush rod in a downward direction, and

position 18 into position 1, and opens the energizing circuit of magnet 451.

The apparatus is now released to normal and ready for use in the building up of another connection.

If a busy potential exists on theline of subscriber 100 when a connector, 400 seizes the same, the potential on test terminal 443 is reduced so as to prevent the energization of test relay 444 in position 8 of sequence switch 410. A circuit is therefore closed from grounded battery through the winding of relay 407, conductor 406, sequence switch contacts 460 and 461, and the lower armature and back contact of relay 444 to ground. Relay 407 becomes energized and closes a circuit from ground through its left-hand armature and front contact, sequence switch contacts 408 and 441, and the power magnet of sequence switch 410 to grounded battery, for moving this sequence switch into position 14. Release magnet 451 is now energized, a circuit being closed from grounded battery through the winding of this magnet,

conductor 452, sequence switch contact 462,

and back contact and lower armature of re lay 444 to:ground. Under the control of magnet 451, connector switch '400 isreturned to its normal position, whereupon a circuit is closed from grounded battery through the power magnet of sequenceemployed in the building up of-the connection.

What is claimed is:

1. In a telephone exchange system, a line, answering and calling terminals therefor, a selectively operable switching device, means for extending said line through its answeringterminals to said switching device, a sender for controlling said switching device to select the calling terminals, testing means associated with sald device, means for-rendering said line unselectable, and means independent of said sender and operative while said line is extended to said switching device for rendering the line selectable.

2. In a telephone exchange system, a line, answering and calling terminals therefor, a

switch 410, sequence switch contact 457, conselectively operable switching device, means for extending said line through its answerlng terminals to said switching device, a sender for causing the said switching device to select said calling terminals, testing means associated with said device. means for maintaining an electrical busy potential on sai-xl calling terminals during the extension of and line to sald device and during the initial operation of said device, and means operable independently of said sender only during the i'ompletion of the operation of the device for rendering said electrical busy potential ineffective.

3. In a telephone exchange system, a line, answering and calling terminals therefor, a connector switch arranged to engage said calling terminals, a selector switch arranged to establish a connecting circuit between said answering terminals and said connector, means operative thereupon for rendering said line unsclectable at said calling terminals, testing means associated with said conncctor switch, and means at said selector switch and operable through said connecting circuit for rendering said calling terminals selectable while the line is extemled through its answering terminals.

4. In a telephone exchange system, a plurality of lines, a connectingcircuit, a selector switch for extending a calling line through said circuit, a test circuit for said calling line established upon the extension thereof, a relay for controlling said test circuit, connector adapted to extend said connecting circuit to said calling line, automatic testing means associated with said connector, and means operative only duringthe operation of said connector and prior t) the operation of said automatic testing means for actuating said relay.

5. In a telephone exchange system, a plurality of lines, means including a selector switch and connecting circuits for extending a calling line, means operative upon the extension of the calling line for rendering said line inaccessible to incoming calls, a connector switch, movable contacts for said connector switch in which said connecting circuits terminate, stationary contacts for said switch in which said lines terminate, and means actuated only during the operation of said connector and prior to the completed operation thereof for rendering said calling line accessible.

(i. In a telephone exchange system, a plurality of lines. a selector switch, movable contacts for said selector switch, a connecting circuit one end of which may be extended to said line and the other end to said movable contacts. stationary contacts for said selector switch in which said lines terminate, means operativeupon the extension of said line to said connecting circuit for rendering it unselecta le through said stationary contacts. and automatic means operative only after the extension of said connecting circuit and prior to the extension thereof through said movable and stationary contacts for rendering said last mentioned means inoperative.

7. In a telephone exchange system, a plurality'of lines, a plurality of offices, means for extending a calling line through said ofiices, means for rendering extendedv lines inaccessible, a relay associated with one of said otiices for controlling said last mentioned means, and means associated with another otlice for controlling the operation of said relay.

8. In a telephone exchange system, a plurality of lines, a plurality of oflices, means including selector switches for extending a calling line through said otliccs back to the calling line, means for rendering extended lines inaccessible, a relay for controlling said last mentioned means, and means controllablc from another otlice for actuating said relay prior to the complete extension of said calling line.

9. In a telephone exchange system, a plurality of olliecs, a plurality of lines terminating in one of said oliices, means for extending a calling line through another oil-ice back to the first mentioned ofiice, means for rendering extended lines busy. and means for rendering the extended calling line idle.

10. In a telephone. exchange system, a plurality of lines, connector switches, a selector switch for extending a calling line to one of said connectors, a test circuit for the calling line closed upon the extension thereof for preventing its seizure by said connector, a relay controlling said circuit, means for actuating said relay during the operation of said selecto and during the selection of said line by said connector, and a slowacting relay for controlling said relay to cause the opening of the test circuit only curing the selective operation of said connector.

11. In a telephone exchange system, a plurality of lines, connector switches, a selector switch for extending a calling line to one of said connectors, a test circuit for the calling line closed upon the extension thereof for preventing its seizure by said connector, a relay for controlling said circuit,-means for actuating said relay during the operation of said selector and during the selection of said line by the connector, a slow-acting relay for controlling said relay to cause the opening of the test circuit only during the selective operation of said connector and another slow-acting relay for contrdlling the duration of thelast mentioned operzition of said relay. 5

12. In a telephone exchange system. aiphr rality of lines, connector switches adapted to seize said lines. a selector switch for extending a calling line to one of said con ncctors, means operative upon the extension of the calling line for preventing its seizure by said connector. a relay controlling said means; megn st'or actuating said relay dur-- ing andal' pr the operation of itlltl selector,

means for causing said relay to control said first mentioned means upon its second operation only, and means for controlling the duration of the last mentioned operation of 5 said relay. I

13. In a telephone exchange system, a

plurality of lines, answering and calling terminals for said lines, a calling line signal associated with each of said lines, another signal, means for restoring the calling line signal of a line upon the engagement of the answering terminal of said line, mean for causing the engagement of the calling terminal of said line, and means for actuating both said signals during the operation of said last mentioned means.

14. In a telephone exchange system, a line, answering and calling terminals therefor, a connecting circuit, means for extending one end of said circuit to the answering terminal, means for extending the other end of said circuit to the calling terminal, a busy test circuit for said line established upon the extension of said circuit to its answering terminal, a signal, a relay for controlling said circuit, and another relay provided in said connecting circuit for controlling said relay and signal.

p 15. In a telephone exchange system, a plurality of lines, answering and calling terminal for said lines, a calling line signal associated with each'of said lines, means for restoring the signal of a line upon the engagement of the answering terminal of said line, means for causing the engagement of the calling terminal of said line, and means operative thereupon far actuating said calling line signal. I

16. Ina telephone exchange system a plu- 40 rality of lines, ansn ering and calling terminals for said lines, a calling line signal associated with each of said lines, means for restoring the signa of a line upon the engagement of the answering terminal of said line, means for cal sing the engagement of the calling terminav of said line, means 0perative thereupon, ior actuating said'signal for a certain lengtl of time, and meansfor operating said sign 11 for a different length of time if the call-lug. terminal of said line has not been engaged.

17. In a telephone exchange system, a plurality of lines, at swering and calling terminals for said lint s, a calling line signal associated with eacl. of said lines. another signal,}m eans for re storing the calling line signal of a line upoi the engagement of theanswering terminal )f said line, means for causing the engagement of the calling termi ha] of said line, an 1 means for actuating said signals for varous lengths of time if reta ler.

the calling terminal of said line hasbeen engaged.

18. In a telephone exchange system, a plurality of lines, answering and calling terminals for said lines,- a calling line signal associated with each of said lines, another signal, means for restoring the calling line signal of a line upon the engagement of the answering terminal of said line, means for causing the engagement of the calling ter- 'minal of said line, means for actuating said signals for various lengths-of time if the calling terminal of said line has been engaged, and means for actuating said signals for the same length of time if said terminal has not been engaged.

19. In a telephone exchange system, a line, answering and calling terminals for said line, a connecting circuit, means for extending said circuit to the answering terminal,

. means for extending said circuit to the calling terminal, means for placing a busy potential on said calling terminal upon the engagement of the answering terminal, means for removing said busy condition while said answering terminal is engaged, and means for controlling the duration of operation of said last mentioned means.

20. In a telephone exchange system, a line, a connecting circuit, a plurality of operators positions, means controllable from one position to extend one end of said connecting circuit to said line, means controllable from another position for extending the other end of said connecting circuit to said line, means operative upon the extension of one end of said connecting circuit to the line for rendering the same busy, and

means controllable from both said operators positions for removing the busy test condition from said line when. the other end ofconnecting circuit to said line, andmeans controllable from both said operators positions for rendering said line idle when said mechanism is being operated.

In witness whereof, I hereunto subscribe my name this 15th day of December A. D., 1915.

ALBEIN E. LUNDElJL. 

